Catheter attachment system

ABSTRACT

This connection system has particular application to releasably securing a flexible elastic catheter to a rigid portal outlet stem received in the catheter lumen. The system includes a radial enlargement on the outlet stem and a retainer sleeve that slidably encircles the stem. The sleeve is slidable along the stem between a clamping position wherein it tightly engages around the stem enlargement and the segment of catheter encircling same at a circular contact surface and a release position wherein it is spaced from the catheter segment. The system assures a secure, fluid-tight connection of the catheter to the stem and provides strain relief for the catheter.

This invention relates to a catheter. It relates more particularly toimproved means for connecting a flexible infusion catheter to a sourceof infusate.

BACKGROUND OF THE INVENTION

The treatment of certain diseases of the human body often requires theshort-term or long-term infusion of drugs, blood products or nutritionalor other fluids into the patient's venous or arterial system orperitoneal or epidural space. While such fluids can be administeredextracorporeally by transcutaneous injection, in some cases, as when aparticular patient's regime requires repeated access for drug infusion,or where infection is of acute concern, it is desirable to provide thepatient with a totally implanted infusion system.

Such a system includes an injection portal which is an infusate chamberimplanted subcutaneously and placed on the chest wall or otherconvenient. body location. The portal is fitted with a needle-penetrableseptum which is located directly under the skin by which drugs or otherfluids may be introduced into the portal by transcutaneous injectionthrough the septum. The portal has a fluid outlet tube or stem which isconnected to one end of a flexible catheter which leads to the infusionsite which is usually a blood vessel or particular body cavity, e.g.,the peritoneal cavity. Since the system is completely implanted, itreduces the risk of infectious complications and allows drug infusionwhich is targeted to the specific patient malady. Even though thedelivery system may be implanted for a long period, the patient remainsambulatory and can be treated on an out-patient basis and the systemdoes not interfere with the normal daily activities of the patient.

A similar prosthesis can be used to draw blood from an artery or veinfor blood sampling purposes.

Since an implantable device of this type may remain in the patient'sbody for many months, it is essential that the connection or attachmentof the catheter to the portal remain secure and fluid-tight during theentire period of implantation. If the connection should fail or if thereshould be an infusate leak at that location, the infusate dose requiredto treat the patient which is injected into the portal will not beconducted to the targeted infusion site in the patient's body. Rather,some or all of the infusate will be dispensed at the site of the portaland could cause complications at that body location. In this connection,it should be appreciated that after a drug delivery system is implanted,the catheter is subjected to various stresses and strains due tomovements of the patient's body, weight changes, etc. These arereflected in tensile and twisting forces at the connection of thecatheter to the portal outlet which tend to upset the integrity of thatunion.

In an attempt to avoid this leakage problem and the attendantcomplications, various steps have been taken to strengthen theconnection between the catheter and the portal. These include theproviding of raised circular rings or ribs on the portal outlet stemover which the catheter wall is stretched. These lines of localizedresilient engagement resist sliding movements of the catheter from theportal stem. In some systems, the connection is made somewhat moresecure by providing a locking ring or bushing which encircles thecatheter and is releasably captured on the catheter segment engaged onthe portal stem by the raised ribs thereon.

We have found, however, that these prior catheter connections are notentirely satisfactory. Sometimes the tensile forces exerted on thecatheter due to movements of the patient still suffice to separate thecatheter from the portal or to tear the catheter at that point ofconnection because of a poor distribution of stresses on the catheterwall. Certain prior systems are disadvantaged in that it is quitedifficult to connect the catheter to the portal outlet stem. This isbecause that stem is often very small (e.g. 1 mm OD), and to make theconnection, the stem must be threaded into the end of the catheter lumenwhich is itself equally small. Furthermore, when inserting the portalstem into the catheter, if one is not quite careful, the catheter willbe punctured by the end of the stem which, being so small, constitutes asharp point. Certain prior systems are disadvantaged in that they haveloose parts that are hard to handle and can be lost. This is because thesystem requires a separate lock that must be put on the catheter beforethe connection to the stem is made. These lock parts are small and easyto drop or lose.

In addition, it should be kept in mind that it may be necessary todisconnect the catheter from an already implanted injection portal inthe event that the catheter has to be replaced for one reason oranother. For example, it sometimes happens that the catheter lumenbecomes clogged by clots or other debris. Therefore, it is desirablethat any connection between the catheter and the portal be separablefrom the portal with a minimum amount of effort and finger manipulationby the surgeon who must make that repair subcutaneously. The priorcatheter connection or attachment systems of which applicant is aware,do not facilitate such ready connection and disconnection of thecatheter to and from the portal.

SUMMARY OF THE INVENTION

Accordingly, the present invention aims to provide an improved catheterattachment system.

Another object of the invention is to provide a catheter attachmentsystem which is very strong, yet which can be released quite easily ifthe need should arise.

Another object of this invention is to provide a catheter connectionsystem which has no loose part that can be lost.

Another object of the invention is to provide a catheter connectionwhich is specially adapted for use in an implantable infusion system forjoining the catheter to an injection portal.

Yet another object of the invention is to provide an attachment systemof this type which minimizes localized stresses on the catheter in theregion of the attachment.

Other objects will, in part, be obvious and will, in part, appearhereinafter.

The invention accordingly comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the following detailed description, and the scope of theinvention will be indicated in the claims.

The catheter attachment or connection system of interest here may beused in any application where it is necessary to releasably connect theend of a flexible resilient catheter or other tube to a stem, tube orrod by inserting the stem, tube or rod into the end of the catheter.Since the invention has particular application to the connection of acatheter to the outlet stem of an implantable injection portal, we willdescribe the invention in this context. It should be understood,however, that the invention may be applied to other applications wheresimilar flexible tube-to-rigid tube connections are required.

Briefly, the present attachment system involves the coaction andcooperation of a flexible resilient catheter, a relatively rigid stem ortube onto which the catheter is slid to effect the connection and aspecially designed, locking retainer which encircles the stem andcatheter on the stem. The system provides strain relief to the catheterand minimizes localized stresses on the catheter due to tensile andother forces exerted on the catheter in use.

The stem component of the system is formed with an axially symmetricradial enlargement. This enlargement takes the form of athree-dimensional bulb located adjacent to the distal end of the stem.The distal end segment of the stem beyond the enlargement has a diameterwhich is approximately the same as the diameter of the lumen in thecatheter being connected to the stem with the enlargement beingappreciably larger than that lumen.

When the catheter, which is the second component of the system, is slidonto the stem, the elastic wall of the catheter stretches outward asrequired to accommodate the larger diameter stem enlargement. Thus, whenthe end segment of the catheter has received the full extent of thestem, the catheter resiliently engages the outer surface of the stem andconforms closely to the enlargement thereof.

The third component of my connection system, namely the retainer, is asleeve or ring which loosely encircles the proximal end segment of theportal stem. The sleeve is free to move back and forth along the stem,but it cannot come off the stem due to its engagement with a flangeadjacent to the proximal end of the stem. When the catheter is slid ontothe stem over the stem enlargement it is guided into the sleeve untilthe end of the catheter butts against the stem flange. When that sleeveis slid outward along the stem, the sleeve captures the catheter againstthe stem enlargement.

As will be described shortly in greater detail, when the retainercomponent of my connection system is seated on the portal stem so thatit captures the catheter thereon, there results a very secure connectionof the catheter to the stem. Even very strong pulling, twisting andbending forces exerted on the catheter are unable to disconnect thecatheter from the stem or to break the fluid-tight integrity of thatconnection. Actually, as we will see, such forces enhance thatconnection.

The catheter connection system described here is also quite easy andinexpensive to manufacture, being composed of simple metal parts whichcan be fabricated in quantity at minimum cost. Also, the connection iseasy to make and to release, even if that needs to be done in the caseof an injection portal already implanted in the body. In other words,the present apparatus facilitates sliding a catheter onto the end of aportal outlet stem and into the locking sleeve to secure the catheter tothe stem with no loose parts. Also, simple finger movements suffice tomanipulate the connector's locking ring to release the catheter from thestem. Consequently, the present attachment system could be usedconveniently wherever it is necessary to releasably connect a flexiblecatheter or other tube to a relatively rigid rod or stem.

BRIEF DESCRIPTION OF THE DRAWING

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing, in which:

FIG. 1 is an isometric view of an implantable injection portalincorporating a catheter attachment system made in accordance with thisinvention;

FIG. 2 is an exploded side elevational view on a much larger scale andwith parts broken away showing the catheter attachment system in itsunlocked position; and

FIG. 3 is a side elevational view showing the connection system in itslocked position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 of the drawing, my catheter attachment system,indicated generally at 10, is shown connecting the proximal end of acatheter 12 to the tubular outlet stem 14 of an implantable injectionportal 16. The portal is made of a material such as titanium and in useit is implanted at a convenient location in the body, such as on thechest wall. This portal might be used, for example, to conduct infusateto a vein leading to the heart. Usually, small eyes 16a are providedaround the base of the portal through which sutures may be passed toanchor the portal to the chest wall. The portal also includes a septem16b composed of a suitable resilient, needle-penetrable material, suchas silicone rubber.

When the portal is implanted, the septum is situated directly under thepatient's skin so that infusate can be introduced into the portal bytranscutaneous injection through the septum. The infusate thereuponflows through the portal outlet stem 14 to the catheter 12 whose distalend is placed at a selected infusion site in the body, such as a bloodvessel or a body cavity such as the peritoneal cavity. Catheter 12 ismade of a flexible, resilient biocompatible material, such as siliconerubber. The inside diameter of the catheter, which corresponds more orless to the nominal outside diameter of portal stem 14, may varydepending upon the particular application, from, say 0.5 to 3.0 mm.Likewise, the volume of the portal 16 may vary from, say, 0.4 ml to 1.0ml.

Referring now to FIGS. 1 and 2 of the drawing, connection system 10 iscomposed of three distinct parts or components. These include theproximal end segment 12a of the catheter, the portal outlet stem 14 anda special locking retainer shown generally at 18. The tubular stem 14 isformed with a radial enlargement 22 along its length. In the systemembodiment depicted herein, the enlargement 22 is located adjacent tothe outer or distal blunt end segment 14a of the stem 14 and it has thegeneral form of a barrel with two back-to-back frustoconical segments22a and 22b. The enlargement has a relatively large, rounded shoulder22c midway along its length, i.e. between segments 22a and 22b whosediameter is appreciably larger than the inside diameter of catheter 12.The enlargement 22 tapers from that shoulder to stem end segment 14a andto a longer stem segment 14b closer to the portal 16 housing. The innerend of stem segment 14b leads to a much larger proximal stem segment 14cprojecting from the wall of the portal housing. For reasons to bedescribed later, a radial flange 24 is provided at the boundary of stemsegments 14b and 14c. The flange has a radial outer or distal surface24a and a beveled inner or proximal surface 24b. The diameter of stemsegment 14a may be somewhat smaller than the inside diameter of thecatheter to aid in initiating catheter engagement, i.e. in aligning theproximal end 22a of the catheter with the stem end segment 14a. Thediameter of stem segment 14b is somewhat larger than the diameter of thecatheter so that a fluid tight seal is produced between that segment andthe catheter.

The shape of the enlargement 22 is such that the stem end segment 14aand the frustonconical segment 22b of the enlargement 22 can beintroduced into the end of the catheter segment 12a for a distancecorresponding to about half the enlargement diameter without extendingor stretching the catheter wall. Further penetration of the stem 14 intothe catheter segment 12a results in the catheter wall stretching ordeforming to accommodate enlargement 22, particularly shoulder 22c. Thatis, the catheter 12, which is typically silicone rubber, is veryresilient. Thus, when catheter segment 12a is engaged fully on stem 14as shown in FIG. 3, i.e. with the end of the catheter engaging flange24, due to the resiliency of the catheter material, the catheter segmentassumes the exact shape of outlet stem 14, including its enlargement 22and stem segments 14a and 14b.

As best seen in FIGS. 2 and 3, the locking retainer 18 is a generallycylindrical sleeve-like member which is slidably engaged on the stem 14.Retainer 18 is an easily fabricated, metal (e.g. titanium) or moldedplastic part. The inside diameter of the retainer is slightly largerthan that of stem flange 24 and its length is comparable to the combinedlengths of stem segments 14b and 14c. The inner or proximal end of theretainer is necked down to form an inwardly extending circular flange orrib 18a which overhangs stem flange 24 and is oriented at more or lessthe same angle as the bevelled surface 24b of that flange.

The outer or distal end of retainer 18 has a reduced inner diameter thatcreates a circular inner rib, flange or ledge 18b on the retainer. Also,that end of the retainer is bevelled to provide a flared or bevelledsurface 18c which extends from the inner edge of ledge 18b toward theouter wall of the retainer. As best seen in FIG. 2, the ledge 18b andbevelled surface 18c together produce a structure at the distal end ofthe retainer which, in crosssection, has the general shape of an annularbarb whose blunted nose 18d projects toward stem 14. When the retainerand stem are coaxial, the flare angle of surface 18c, as measured fromthe stem 14 longitudinal axis or centerline, is appreciably greater thanthat of enlargement segment 22a so that when catheter 12 is tensioned,nose 18d will bite into the catheter wall creating strong retentionforces. For example, the former angle may be 45° and the latter angle20°.

Retainer 18 is slidable along stem 14, with the stem flange 24 providinga bearing surface, between an unlocking position shown in FIG. 2established by the engagement of the retainer flange 18a against theportal housing, wherein the retainer surface 18c and nose 18d are spacedappreciably from enlargement segment 22a and a locking position shown inFIG. 3 wherein the surface 18c and nose 18d are situated close tosegment 22a, with the nose lying about halfway along the length of thatsegment. The stem flange 24, in addition to functioning as a stop forcatheter 12 and as a bearing surface for the retainer as describedabove, also prevents the retainer 18 from sliding off the stem 14 byengaging the retainer flange 18a. A pair of diametrically opposite holes26 are provided in the wall of retainer 18 to make it easier for thesurgeon to see that the catheter is completely in place and abuttingflange 24 inside the locking retainer.

The connection of catheter 12 to stem 14 can be made quite easily withone hand, even when the surgeon has no clear view of the connectionsite. To effect the connection, the surgeon grasps the end of thecatheter and, feeling with his fingers, slides the catheter onto the endsegment 14a of portal stem 14. He then pushes the end of the catheterover the stem enlargement 22 and into sleeve 18 until the catheter endis stopped by the stem flange 24. He can verify that the catheter isseated properly by observation through the retainer holes 26. Thesurgeon then pulls back gently on locking retainer 18 until the retainernose 18d engages against and compresses the outer surface of cathetersegment 12a as shown in FIG. 3. Most desirably, the inner diameter ofretainer ledge or flange 18b, or more particularly of its nose 18dshould be less than the diameter of enlargement shoulder 22c in whichevent, retainer flange 18a could be dispensed with. However, thiscreates manufacturing difficulties. To avoid these difficulties, thediameter of retainer nose 18 d is dimensioned to be smaller than thediameter of stem enlargement 22 plus twice the wall thickness of thecatheter segment stretched over that segment 14b.

When the connection is made and locked as shown in FIG. 3, it ispractically impossible to pull catheter 12 from the portal stem 14. Anypulling or twisting forces applied to the catheter only serve to tightenthe connection between the catheter and the stem. That is, when catheter12 is pulled away from portal 16, it pulls retainer 18 along with it toa locking position against enlargement segment 22a at a circular area ofcontact C (FIG. 3). Increased tensile forces only serve to pull theretainer more tightly against segment 22a at contact surface C.Resultantly, the retainer surface 18c and nose 18d are moved closer tothe frustoconical segment 22a of enlargement 22 so that nose 18d clampsor bites even more firmly into the stretched catheter wall therebyfurther increasing the retention forces on the catheter. Accordingly, afrustoconical catheter segment is sandwiched or compressed ever moretightly between enlargement segment 22a and the retainer surface atcontact surface C, as clearly seen in FIG. 3.

That engaged and compressed segment of the catheter has a relativelylarge area so that the stresses on the catheter due to such pulling andtwisting forces are distributed uniformly over that segment, thusavoiding localized strains in the catheter wall that might tend topromote tears or punctures in that wall. Consequently, there is verylittle likelihood of the catheter pulling away from the portal outletstem 14 or tearing due to movements of the patient in which theprosthesis is implanted. Indeed, the integrity of the connection system10 should be maintained for the entire period of implantation.

However, if it should become necessary to replace the catheter 12 forsome reason, the present system 10 facilitates that as well. To removethe catheter, the surgeon simply holds the retainer 18 back or urges ittoward the portal housing while pulling the catheter from stem 14. Sincethe retainer cannot move outward, it cannot clamp the catheter segment12a to enlargement 22, so the catheter will pull off readily, leavingthe stem 14 ready for a new catheter. Indeed, the same locking retainerand portal stem can be assembled and disassembled many times if need be.

It will be seen from the foregoing, then, that my catheter connectionsystem establishes a reliable, releasible, fluid-tight and easily madejoint or connection between the end of a catheter or other flexible tubeand a rigid tube, stem or other fluid pathway. The system's lockingretainer is easy to manipulate when connecting and disconnecting thecatheter from the tube or stem, even if the surgeon's view isobstructed. Yet the components of the system are relatively easy andinexpensive to make so that the providing of this secure connection doesnot materially increase the overall cost of the injection portal orother prosthesis incorporating the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:
 1. Connection apparatus comprisingA. a relatively rigid elongated stem, said stem having a free end, an opposite end and means defining an enlargement on the exterior surface of the stem at a selected location between said ends; B. a flexible elastic tube having a lumen for elastically receiving a lengthwise segment of said stem including said enlargement thereof, said enlargement having a maximum diameter appreciably larger than that of the lumen so that when said stem segment is received in the lumen, said tube is stretched conformingly around said stem enlargement; and C. tubular retainer means slidably received on said stem between said tube opposite end and said enlargement, said retainer means including radially inwardly extending rigid flange means at or near a distal end of said retainer means that faces said enlargement, said flange means having a fixed diameter that is less than the maximum diameter of said stem segment plus twice the wall thickness of said tube when engaged elastically on said stem segment so that when said stem segment is received in the tube lumen and said retainer means are slid toward the free end of said stem, said flange means compressively engage the elastically stretched wall of said tube at a contact surface that encircles a segment of said enlargement.
 2. The connection apparatus defined in claim 1 wherein said stem segment is received in said lumen.
 3. The connection apparatus defined in claim 1 wherein the distal end of said retainer means is bevelled outwardly adjacent to said flange means at a selected bevel angle.
 4. The connection apparatus defined in claim 1 wherein the enlargement segment encircled by said flange means is flared at a selected flare angle.
 5. The connection apparatus defined in claim 4 wherein the flare angle is less than said bevel angle as measured from the longitudinal axis of said stem.
 6. The connection apparatus defined in claim 5 wherein said enlargement comprises a pair of integral generally frustoconical sections arranged base-to-base and said flange means encircle a proximal frustoconical section adjacent to said stem opposite end.
 7. The connection apparatus defined in claim 6 wherein said retainer means comprise a sleeve encircling said stem and movable therealong between a first position wherein said flange means closely encircle the proximal frustoconical section and a second position wherein said flange means do not do so thereby permitting said tube to be slid onto and from said stem segment.
 8. The connection apparatus defined in claim 1 wherein said flange means clamp or bite into the tube wall when they compressively engage the tube wall so that when the tube is tensioned, the resultant lengthwise movement of the tube wall along the stem pulls the retainer means further toward the free end of the stem thereby clamping the tube more tightly between said flange means and said stem enlargement.
 9. The connection apparatus as defined in claim 1 and further including coacting means on said stem and said retainer means for preventing said retainer means from sliding beyond the free end of said stem.
 10. The connection apparatus defined in claim 9 wherein said coacting means compriseA. detent means adjacent to said opposite end of the stem; and B. projecting means on said retainer means that project toward said stem and engage said detent means before said retainer means can slide appreciably beyond said enlargement.
 11. The connection apparatus defined in claim 1 whereinA. said stem is generally cylindrical; B. said stem enlargement has a circular cross section and axial symmetry; and C. aid retainer means comprise a cylindrical sleeve with a radially inwardly extending circular flange at its distal end that constitutes said flange means, said flange having a minimum diameter that is not appreciably greater than the maximum diameter of said enlargement.
 12. Apparatus for connecting a relatively rigid elongated stem having a free end to a flexible tube having a lumen for elastically receiving a lengthwise segment of the stem, said apparatus comprisingA. a radial enlargement at a selected location along the stem; B. a generally cylindrical sleeve slidably received on the stem for releasably clamping around a flexible tube segment encircling said enlargement, said sleeve having an inner radial rigid rib or flange at its distal end facing said enlargement and whose diameter is fixed and not appreciably larger than the maximum diameter of said enlargement; and C. coacting means on the stem and sleeve for preventing the sleeve from sliding beyond the free end of the stem.
 13. The apparatus defined in claim 12 whereinA. the opening into the distal end of said sleeve is flared; and B. said rib or flange is located at the inner end of said flare.
 14. The apparatus defined in claim 13 where said enlargement is composed of a frustoconical section facing said sleeve, said section having a flare angle that is less than the flare angle of the sleeve opening as measured from the longitudinal axis of said stem.
 15. The apparatus defined in claim 14 wherein the former flare angle is about half the latter flare angle.
 16. The apparatus defined in claim 12 wherein the diameter of said sleeve rib or flange is less than the maximum diameter of said stem segment plus twice the thickness of the lumen wall elastically stretched around the stem segment. 